Finding a Primary Key Constraint on the fly in SQL Server 2005 - sql

Question

I have the following SQL:
ALTER TABLE dbo.PS_userVariables DROP CONSTRAINT PK_PS_userVariables;
ALTER TABLE dbo.PS_userVariables ADD PRIMARY KEY (varnumber, subjectID, userID, datasetID, listid, userVarTitle);
Since I have multiple environments, that PK_PS_userVariables constraint name is different on my different databases. How do I write a script that gets that name then adds it into my script?

Answer 1

While the typical best practice is to always explicitly name your constraints, you can get them dynamically from the catalog views:
DECLARE #table NVARCHAR(512), #sql NVARCHAR(MAX);
SELECT #table = N'dbo.PS_userVariables';
SELECT #sql = 'ALTER TABLE ' + #table
+ ' DROP CONSTRAINT ' + name + ';'
FROM sys.key_constraints
WHERE [type] = 'PK'
AND [parent_object_id] = OBJECT_ID(#table);
EXEC sp_executeSQL #sql;
ALTER TABLE dbo.PS_userVariables ADD CONSTRAINT ...

Answer 2

SELECT
A.TABLE_NAME,
A.CONSTRAINT_NAME,
B.COLUMN_NAME
FROM
INFORMATION_SCHEMA.TABLE_CONSTRAINTS A,
INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE B
WHERE
CONSTRAINT_TYPE = 'PRIMARY KEY'
AND A.CONSTRAINT_NAME = B.CONSTRAINT_NAME
ORDER BY
A.TABLE_NAME
Ref: Pinal Dave # http://blog.sqlauthority.com/2008/09/06/sql-server-find-primary-key-using-sql-server-management-studio/

Answer 3

DECLARE #TableName varchar(128)
DECLARE #IndexName varchar(128)
DECLARE #Command varchar(1000)
SET #TableName = 'PS_userVariables'
SELECT #IndexName = si.name
FROM sys.tables st
JOIN sys.indexes si ON st.object_id = si.object_id
WHERE st.name = #TableName
AND si.is_primary_key = 1
SET #Command = 'ALTER TABLE dbo.' + QUOTENAME(#Tablename) + ' DROP CONSTRAINT ' + QUOTENAME(#IndexName) + ';
ALTER TABLE dbo.' + QUOTENAME(#Tablename) + ' ADD PRIMARY KEY (varnumber, subjectID, userID, datasetID, listid, userVarTitle);'

Answer 4

My use case was updating primary key constraint names generated by Entity Framework 6 to match the primary key naming convention of Entity Framework Core.
As EF uses migrations, I created both an Up and Down migration script, and created a temporary long-lived table to store the old and new constraint names so that I could roll back if needed.
This is the SQL I used to update the primary key constraint names:
-- create a temporary long-lived table
-- it can be deleted when rollback is no longer needed
CREATE TABLE dbo.__OldPrimaryKeyConstraintNames (
SchemaName NVARCHAR(128) NOT NULL DEFAULT 'dbo',
TableName NVARCHAR(128) NOT NULL,
OldPrimaryKeyConstraintName NVARCHAR(128) NOT NULL,
NewPrimaryKeyConstraintName NVARCHAR(128) NOT NULL
);
-- create a temporary table to hold the data for the script
DECLARE #tbl TABLE (SchemaName NVARCHAR(3), TableName NVARCHAR(128), PrimaryKeyConstraintName NVARCHAR(128));
-- get all primary key constraint names as well as it's schema and table
INSERT INTO #tbl
SELECT SCHEMA_NAME(pk.schema_id), t.name, pk.name
FROM sys.key_constraints pk
INNER JOIN sys.objects t on t.object_id = pk.parent_object_id
WHERE pk.type = 'PK'
-- row count used for iterating through #tbl
DECLARE #RowCount INT = (SELECT COUNT(*) FROM #tbl);
-- variables used when used for iterating through #tbl
DECLARE #SchemaName NVARCHAR(128)
DECLARE #TableName NVARCHAR(128)
DECLARE #OldPrimaryKeyConstraintName NVARCHAR(128)
DECLARE #NewPrimaryKeyConstraintName NVARCHAR(128)
DECLARE #RenameSql NVARCHAR(MAX)
WHILE #RowCount > 0 BEGIN
-- get the primary key constraint name, schema, and table name for this iteration
SELECT #SchemaName = SchemaName, #TableName = TableName, #OldPrimaryKeyConstraintName = PrimaryKeyConstraintName, #NewPrimaryKeyConstraintName = CONCAT('PK_', TableName)
FROM #tbl
ORDER BY PrimaryKeyConstraintName DESC OFFSET #RowCount - 1 ROWS FETCH NEXT 1 ROWS ONLY;
-- store the old and new primary key constraint names
INSERT __OldPrimaryKeyConstraintNames (SchemaName, TableName, OldPrimaryKeyConstraintName, NewPrimaryKeyConstraintName)
VALUES (#SchemaName, #TableName, #OldPrimaryKeyConstraintName, #NewPrimaryKeyConstraintName)
-- perform the rename
SET #RenameSql = 'sp_rename ' + '''' + #SchemaName + '.' + QUOTENAME(#OldPrimaryKeyConstraintName) + '''' + ', ' + '''' + #NewPrimaryKeyConstraintName + ''''
EXEC sp_executeSQL #RenameSql
-- move to the next row
SET #RowCount -= 1;
END
After running this script, dbo.__OldPrimaryKeyConstraintNames should be populated with the old and new constraint names.
This allows us to revert the renaming if required for whatever reason.
This is the SQL I used to revert the primary key constraint names:
-- create a temporary table to hold the data for the script
DECLARE #tbl TABLE (SchemaName NVARCHAR(3), OldPrimaryKeyConstraintName NVARCHAR(128), NewPrimaryKeyConstraintName NVARCHAR(128));
-- get the old and new constraint names as well as it's schema and table name
INSERT INTO #tbl
SELECT SchemaName, OldPrimaryKeyConstraintName, NewPrimaryKeyConstraintName
FROM dbo.__OldPrimaryKeyConstraintNames
-- row count used for iterating through #tbl
DECLARE #RowCount INT = (SELECT COUNT(*) FROM #tbl);
-- variables used when used for iterating through #tbl
DECLARE #SchemaName NVARCHAR(128)
DECLARE #TableName NVARCHAR(128)
DECLARE #OldPrimaryKeyConstraintName NVARCHAR(128)
DECLARE #NewPrimaryKeyConstraintName NVARCHAR(128)
DECLARE #RenameSql NVARCHAR(MAX)
WHILE #RowCount > 0 BEGIN
-- get the old and new constraint name and it's schema for this iteration
SELECT #SchemaName = SchemaName, #OldPrimaryKeyConstraintName = OldPrimaryKeyConstraintName, #NewPrimaryKeyConstraintName = NewPrimaryKeyConstraintName
FROM #tbl
ORDER BY OldPrimaryKeyConstraintName DESC OFFSET #RowCount - 1 ROWS FETCH NEXT 1 ROWS ONLY;
-- revert the rename
SET #RenameSql = 'sp_rename ' + '''' + #SchemaName + '.' + QUOTENAME(#NewPrimaryKeyConstraintName) + '''' + ', ' + '''' + #OldPrimaryKeyConstraintName + ''''
SELECT #RenameSql
EXEC sp_executeSQL #RenameSql
-- move to the next row
SET #RowCount -= 1;
END
-- drop the temporary long-lived table as it is not required
DROP TABLE IF EXISTS dbo.__OldPrimaryKeyConstraintNames